Dental appliance



June 5, 1956 c. R. MCCULLY ET AL DENTAL APPLIANCE Filed Oct. 20, 1954 14.Fzgz

Charles Poland McCu/{y Edward 5'. De Marsh United States Patent DENTALAPPLIANCE Charles Roland McCully, Chicago, Ill., and Edward S. De Marsh,Seattle, Wash.

Application October 20, 1954, Serial No. 463,539

7 Claims. (Cl. 32-40) The present invention is concerned with animproved dental appliance and is particularly concerned with an improvedmechanism for assuring uniform quality and composition in dentalamalgams used as fillings in teeth.

In the manufacture of dental amalgams, it is customary to compound thesilver or silver alloy with an excess of mercury, after which thecombination is very thoroughly mixed to assure uniformity in the finalcomposition. When this has been done, it is common practice to place theamalgam on a small piece of cloth and then twist the amalgam in thecloth or possibly even squeeze the amalgam in the folded cloth with apair of pliers or other suitable instrument. The purpose of thisoperation is to express excess mercury out of the composition and intothe pores of the cloth.

As might be expected, the above described operation for removing excessmercury does not produce amalgams of uniform composition, as it isimpossible to control accurately the pressure on the amalgam while themercury is being expressed from it. Hence, it frequently occurs that twosucceeding amalgams made from identi cally the same original compositionmay have considerably difierent properties due to the differences inpressure used in expressing the excess mercury. This difference inpressure ultimately shows up as differences in the mercury content ofthe final amalgam.

An object of the present invention is to provide an improved device forexpressing mercury from freshly compounded dental amalgams underconditions of accurate and reproduceable pressures.

Another object of the invention is to provide an improved device forexpressing mercury from amalgams which is substantially automatic inoperation.

Still another object of the present invention is to provide an improveddevice of the character described which is simple in structure and inoperation and yet capable of producing a series of amalgams of identicalcomposition after the excess mercury has been removed.

A further description of the present invention will be made inconnection with the attached sheet of drawings which illustrates apreferred form thereof;

In the drawings:

Figure l is a view in elevation of the device illustrating the manner inwhich the device is secured to a supporting surface;

Figure 2 is a fragmentary cross-sectional view of the interior of thehousing of the device, the view being taken at the time the amalgam isfirst introduced into the pressure chamber; and

Figure 3 is a view similar to Figure 2, but illustrating the conditionof the elements at the time the mercury is being expressed from theamalgam.

In the dental appliance of the present invention, the amalgam,containing an excess of mercury, is first conveniently wrapped in asmall piece of porous fabric which serves the dual function of makingthe amalgam easier to handle and providing a medium for absorbing theexpressed mercury. The amalgam, wrapped in its 2,748,482 Patented June5, 1956 fabric cover, is then placed into a pressure chamber formed in asuitable housing. Included within the pressure chamber is a resilientlyflexible membrane subject to variations in fluid pressure in thepressure chamber. The wrapped amalgam is preferably disposed between theouter side of membrane and a stationary part of the housing.

The pressure in the pressure chamber is adjusted and controlled by theoperation of a reciprocating piston which may be actuated to draw ahydraulic fluid from a suitable reservoir into the cylinder in which thepiston reciprocates, and upon the downward stroke of the piston to forcethe hydraulic fluid into the pressure chamber. In a preferred form ofthe invention, means are also provided to bleed off some of the fluidunder pressure being introduced into the chamber when the desiredpressure is reached.

Turning now to the specific embodiment of the invention illustrated inthe drawings, it will be observed from Figure 1 that the housing mayconsist of a G-shaped bracket 10 arranged to engage the surface of atable 11 or other supporting structure with a threaded bolt 12 supplyingsuflicient pressure against the bottom edge of the table surface 11 tohold the frame member 10 rigidly against the table 11.

As best seen at Figures 2 and 3, the frame member 16 is provided with aninternal bore which defines a cylinder 13 in which a headed piston 14 isarranged to reciprocate. The head 14a of the piston 14 is suitablynotched to receive an 0 seal ring 16 to provide a fluid seal between thepiston 14 and its cylinder 13. The piston 14 is free to reciprocatewithin the cylinder 13 to a'limit defined by the position of a hollowbushing 17 threaded into the frame member 10.

The outer end of the piston 14 is pivotally secured to a pin 18 carriedby an operating lever 19. As illustrated in Figure l, the operatinglever 19 may be quite long in comparison with the stroke of the piston14.

The fulcrum for the operating lever 19 is provided by means of a pin 21secured to a link 22 which in turn is pivotally secured to a pin 23carried by the frame member 10. As evident from Figures 2 and 3, thepresence of the link 22 permits the piston 14 to reciprocate freely inan upward direction within the cylinder 13. It will also be seen fromFigure 1 that the length of the operating lever 19 is considerablygreater than the distance between the pin lfiand the pin 21, so that aneifective mechanical advantage is provided.

The cylinder 13 is arranged to be placed in fluid communication with areservoir 24 of hydraulic fluid such as oil 25. A port 26 provides thisfluid communication when the pressure conditions are such that a checkvalve, including a ball 27 and a helical spring 28 located in the port26 is open to permit flow of the hydraulic fluid from the reservoir 24into the cylinder 13.

The pressure chamber previously mentioned, is, in the form of theinvention illustrated in the drawings, formed 'by a top plate 30pivotally secured to the frame member lil by means of a hinge 31. Thetop plate 30 cooperates with a hollowed metal insert 32 which fits intoa suitable recess provided in the top of :the frame member 10. includedwithin the hollowed-out portion of the insert 32 is a resilientlyflexible membrane 33 composed of rubber or similar material, themembrane 33 having an edge portion 33a securely received and clampedbetween the bottom of the insert 32 and the base of the recess in theframe member 10 which receives the insert 32. The inner walls of themembrane 33 define a pressure chamber 34 into which the hydraulic fluidis pumped during the operation of the device.

An eyebolt 36 engages a pin 37 in the frame member 10 and is receivedwithin a slot 38 formed in the :top

- 3 plate 30. A wing nut 39 engages the threaded end of the eyebolt 36to hold the top plate 30 against displacement when pressure is beingapplied in the pressure chamber.

A pressure chamber 34 communicates with the cylinder 13 through a port41. Another check valve member, including a ball 42 and a helical spring43 is provided to prevent return flow from the pressure chamber 34 tothe cylinder 13. The spring 43 normally urges the 'ball 42 into seatingrelation in a reduced diameter portion of the port 41.

As a means for controlling the pressure in the pressure chamber 34, Wemay provide another valve element including a needle valve member 44having a conical seati-ng face 46 arranged to close off fluidcommunication between the reservoir 24 and a port '47 which extends tothe port 41. The needle valve member 44 is freely slidable Within athreaded bushing 57 which is secured in the frame by means of a lock nut48. The needle valve member 44 may, if desired, be provided with aperipheral recess to receive an O-ring 49 which provides a liquid seal.

The needle valve member 44 also has an enlarged flange portion 51 at oneend thereof which serves as a stop to bottom a helical spring 52extending between the end of the bushing 57 and the flange portion 51.As will be evident from the drawings, the spring 52 normally urges theneedle valve seating face 46 into seated relation with the port 47,thereby preventing flow of the hydraulic fluid back into the reservoirby the pumping action of the piston 14 during normal operation. If,however, the pressure in the pressure chamber 41 should exceed apredetermined value, the fluid pressure in the port 47 may be suflicientto unseat the needle valve member 14 and bleed oif some of the pressurefluid back into the reservoir 24. The positioning of the bushing 47within the wall of the frame member 10 provides an accurate means foradjusting the pressure at which the needle valve member 44 will becomeunseated, as this position controls the compression of the spring 52.

In the operation of the device, a freshly compounded amalgam is placedWithin a cloth wrapper 54 and is placed on the top surface of theflexible membrane 33.

The top plate 30 is then clamped down into position, as illustrated inFigure 2, so that the amalgam in its wrapper 54 is disposed between themembrane 33 and the bottom surface of the top plate 30. The operatinglever 19 is then actuated one or more times to draw hydraulic fluid fromthe reservoir 24 into the cylinder 13. The suction provided by theupward movement of the piston 14 is sufiicient to provide a pressuredifferential across the ball 27 of suflicient magnitude to unseat it andpermit the flow of fluid 25 through the port '26 and into the cylinder13.

Downward movement of the piston upon the return stroke of the operatinglever 19 forces the fluid collected Within the cylinder 13 to travelinto the pressure chamber 34 by unseating the ball 42. Return of thehydraulic fluid to the reservoir 24 is prohibited, since the port 47 isclosed off by the position of the needle valve element '44.

The fluid enters and fi'l-ls the pressure chamber 34, causing theflexible membrane '33 to expand in response to this increase inpressure. The pressure is transmitted uniformly along the walls of themembrane, and when the membrane is fully extended, it begins to exert acompressive action against the wrapped amalgam 5'4, squeezing it betweenthe membrane 33 and the lower surface of the top plate 30. Suflicientpressure is built up in this manner to express the desired amount ofexcess mercury from the amalgam. If desired, some means of pressuremeasurement such as a gauge may be included with the pressure chamber 34so that the pressure in that chamber can be exactly reproduced insucceeding runs. Normally, however, the needle valve 44 will control thepressure obtained in the device with suflicient accuracy to makeadditional pressure control means unnecessary.

When the mercury has been expressed, the top cover 30 may be opened byreleasing the latch provided by the eyebolt 36, and the pressure in thepressure chamber 34 relieved by a straight pull on a pin extendingthrough the needle valve element 44. When a pull sufficient tocounteract the action of the spring 52 is applied, the valve element 46is unseated from the port 47 so that the hydraulic fluid may flow fromthe pressure chamber 34 into the port 41, and finally into the reservoir24 through the port 47.

It should be noted that the arrangement of the needle valve member 44provides an automatic pressure limiting system. When the pressure in thechamber 34 has built up to the desired value, the fluid pressure will besuflicient to unseat the conical valve seating face '46 of the needlevalve member 44, thus permitting some of the hydraulic fluid to bleed'back into the reservoir 24.

From the foregoing, it will be apparent that we have herein provided asimple but effective mechanism for controlling the expression of theexcess mercury from dental amalgams. The device is inexpensive tomanufacture and to maintain and provides a convenient means forproducing a series of dental amalgams of uniform concen-tration.

It will be evident that various modifications can be made in thedescribed embodiment .without departing from the principles of thepresent invention.

We claim as our invention:

1. A pressure applicator comprising a housing, means in said housingproviding a reservoir for a hydraulic fluid, means in said housingproviding a cylinder in fluid communication with said reservoir, a checkvalve disposed between said reservoir and said cylinder permitting flowof fluid from said reservoir to said cylinder, a piston reciprocable insaid cylinder, a pressure chamber communicating with said cylinder, acheck valve between said pressure chamber and said cylinder permittingflow of fluid from said cylinder to said pressure chamber zone, and aflexible membrane associated with said pressure chamber and operable inresponse to fluid pressure in said pressure chamber to expand and applypressure against a stationary portion of said housing.

2. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing providing a reservoir for ahydraulic fluid, means in said housing providing a cylinder in fluidcommunication with said reservoir, a check valve disposed between saidreservoir and said cylinder permitting flow of fluid from said reservoirto said cylinder, 2. piston reciprocable in said cylinder, a pressurechamber communicating with said cylinder, a check valve between saidpressure chamber and said cylinder permitting flow of fluid from saidcylinder to said pressure chamber, a flexible membrane associated withsaid pressure chamber and operable in response to fluid pressure in saidpressure chamber to compress an amalgam between said membrane and astationary portion of said housing, and means communicating saidpressure chamber with said reservoir to return fluid from said pressurechamber to said reservoir.

3. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing providing a reservoir for ahydraulic fluid, means in said housing providing a cylinder in fluidcommunication with said reservoir, a check valve disposed between saidreservoir and said cylinder permitting flow of fluid from said reservoirto said cylinder, a piston reciprocable in said cylinder, a pressurechamber communicating with said cylinder and defining a pressure Zone, acheck valve between said pressure chamber and said cylinder permittingflow of fluid from said cylinder to said pressure chamber, a flexiblemembrane associated with said pressure chamber and operable in responseto fluid pressure in said pressure chamber to compress an amalgam be-.wrrav r tween said membrane and a stationary portion of said housing,means communicating said pressure chamber with said reservoir, andadjustably positionable valve means associated with said last namedmeans, and spring means urging said valve means to a closed position.

4. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing defining a cylinder, apiston reciprocable in said cylinder, means in said housing providing areservoir for a hydraulic fluid, means in said housing providing a firstport connecting said reservoir with said cylinder, a first check valvein said first port arranged to permit flow from said reservoir into saidcylinder, a first spring urging said check valve into its closedposition in which said first check valve closes said first port, a coverhingedly secured to said housing, means for locking said cover in oneposition, means in said housing providing a pressure chamber, a flexiblemembrane actuated by differences in fluid pressure in said pressurechamber and underlying said cover, means in said housing providing asecond port connecting said pressure chamber with said cylinder, asecond check valve disposed in said second port and arranged to permitflow from said cylinder into said pressure chamber, and a second springurging said second check valve into its port closing position.

5. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing defining a cylinder, apiston reciprocable in said cylinder, means in said housing providing areservoir for a hydraulic fluid, means in said housing providing a firstport connecting said reservoir and said cylinder, a first check valve insaid first port arranged to permit flow from said reservoir into saidcylinder, a first spring urging said check valve into its closedposition in which said first check valve closes said first port, a coverhingedly secured to said housing, means in said housing providing apressure chamber, a flexible membrane actuated by difierences in fluidpressure in said pressure chamber and underlying said cover, means insaid housing providing a second port connecting said pressure chamberwith said cylinder, a second check valve disposed in said second portand arranged to permit flow from said cylinder into said pressurechamber, a second spring urging said second check valve into portclosing postition, means in said housing providing a third portconnecting said reservoir with said second port, a valve arranged toclose said third port, and means urging said valve into a position inwhich said valve closes said third port.

6. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing defining a cylinder, apiston reciprocable in said cylinder, means in said housing providing areservoir for a hydraulic fluid, means in said housing providing a firstport connecting said reservoir and said cylinder, a first check valve insaid first port arranged to permit flow from said reservoir into saidcylinder, a first spring urging said check valve into its closedposition in which said first check valve closes said first port, a coverhingedly secured to said housing, means in said housing providing apressure chamber, a flexible membrane actuated by differences in fluidpressure in said pressure chamber and underlying said cover, means insaid housing providing a second port connecting said pressure chamberwith said cylinder, a second check valve disposed in said second portand arranged to permit flow from said cylinder into said pressurechamber, a second spring urging said check valve into port closingposition, means in said housing providing a third port connecting saidreservoir with said second port, a needle valve arranged to close saidthird port, means in said housing receiving said needle valve in slidingrelationship, and a spring urging said needle valve into a position inwhich said needle valve closes oif said third port.

7. A device for expressing excess mercury from a dental amalgamcomprising a housing, means in said housing defining a cylinder, apiston reciprocable in said cylinder, means in said housing providing areservoir for a hydraulic fluid, means in said housing providing a firstport connecting said reservoir and said cylinder, a first check valve insaid first port arranged to permit flow from said reservoir into saidcylinder, a first spring urging said check valve into its closedposition in which said first check valve closes said first port, a coverhingedly secured to said housing, means in said housing providing apressure chamber, a flexible membrane actuated by differences in fluidpressure in said pressure chamber and underlying said cover, means insaid housing providing a second port connecting said pressure chamberwith said cylinder, a second check valve disposed in said second portand arranged to permit flow from said cylinder into said pressurechamber, a second spring urging said check valve into port closingposition, means in said housing providing a third port connecting saidreservoir with said second port, a needle valve arranged to close saidthird port, a hollow bushing threaded into said housing and receivingsaid needle valve in sliding relationship, and a spring urging saidneedle valve into a position in which said needle valve closes ofl saidthird port.

References Cited in the file of this patent UNITED STATES PATENTS2,685,189 Watson Aug. 3, 1954

